Solid isocyanatosulfonic acid uretdiones are obtained by the sulfonation of aromatic isocyanates, in liquid form or in solution in organic solvents, generally accumulating in the form of coarse-grained suspensions (cf. for example German Offenlegungsschrift No. 2,524,476). By filtering the suspensions, it is possible to recover the isocyanatosulfonic acid uretdiones in powder form. In many cases, the suspensions of isocyanatosulfonic acid uretdiones in isocyanate or even in organic solvents which are obtained during sulfonation are used for further reactions of the isocyanatosulfonic acids, for example with oxiranes or oxetanes (cf. for example German Offenlegungsschrift No. 2,651,065 or German Offenlegungsschrift No. 2,735,047). Difficulties are involved in handling these suspensions on account of their tendency to sediment. Exact metering is virtually impossible. In addition, the fact that the isocyanatosulfonic acids are characterized by being in a coarse dispersion reduces their reactivity to oxiranes and oxetanes. This results in the production of foams wherein the dispersed phase is not dissolved quickly enough. This applies in particular to suspensions of the dimeric sulfonic acid of isocyanatotoluene or diisocyanatodiphenyl methane in excess tolyene diisocyanate or diisocyanatodiphenyl methane.
Accordingly, the object of the present invention is to provide non-sedimenting dispersions of aromatic isocyanatosulfonic acid uretdiones which do not have any of the disadvantages referred to above.
According to the present invention, this object is achieved for the first time by the process described in detail hereinafter.